Novelty detection for unsupervised continual learning in image sequences

Recent works in the domain of deep learning for object recognition on common image classification benchmarks often address the representation learning problem under the assumption of i.i.d. input data. Although achieving satisfying results, this assumption seems not realistic when agents have to learn autonomously. An autonomous agent receives a continual visual flow of objects which is far from an i.i.d. distribution of objects. Moreover, agents have to construct their representations of the world and adapt to unknown environments, without relying on external sources of information such as labels that would be provided post-classification and are unavoidable when an over-segmentation is done. Then, in order to exploit the learned representation effectively for object recognition, a clear and meaningful relationship w.r.t. real object categories is required, which has been largely neglected in existing unsupervised algorithms. In this paper, we propose a novelty detection method for continual and unsupervised object recognition, as an extension for the recent CURL model, which allows to moderate over-segmentation while preserving accuracy, in order to meet the requirements for autonomy. We experimentally validated our approach on two standard image classification benchmarks, MNIST and Fashion-MNIST, in this unsupervised and continual learning setting and improve the state of the art in terms of cluster purity, which is crucial for subsequent object recognition, since it facilitates clustering when information on ground truth labels is not available for free.